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#1 yock1960

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Posted 10 January 2013 - 08:08 PM

A co-worker of mine told me about a telescope he got from the widow of a former client. He didn't really know anything about it, as he is no astronomer and he never used it; there is no tripod. I told him to bring in some pictures which he did. It was a Celestron SCT, I couldn't tell what exactly, but it looked bigger than a C8. At the time I wasn't particularly interested. While something like that would come in handy occasionally in DSO imaging, it wasn't something that I 'had' to have.

He brought it to work today and now it's sitting just behind me. I mis-judged, it is a C8; not sure what flavor, but from the clock-only drive, it appears to be 'ancient'. It does however look to be in very good shape, having been stored well protected; if not hermetically.

This would be just what I need to amp up my Jupiter imaging! I would de-fork it and put it on one of my GEMs.

Would the Powermate 2.5x be too much for this? What am I missing? I know next to nothing about these scopes!

Of course, he may want more than I want to give for it....who knows...haven't spoken of it yet.

Steve

#2 Timthelder

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Posted 10 January 2013 - 08:48 PM

What a find Steve!

A 2.5x will do just fine (I use one on my 9.25") butI do recommend a high quality SCT dual-crayford focuser.(JMI maybe? or one like your moonlite for a SCT)

A dovetail rail mounted on that beauty and you'll be set for some planetary.

Cheers

#3 zAmbonii

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Posted 10 January 2013 - 08:50 PM

Make sure the corrector plate has no cracks and the mirror looks fine. I've been using a newer C8. With my webcam with 5.6um pixels I was imaging with a 3x barlow. With the ASI120MM and its 3.75um pixels it gives me the same image size with a 2x barlow.

Unfortunately, with your Powermate you cant just put in an extension to get 3x, the power goes down with increasing distance to the chip. I just used a plain old Orion 3x tri-mag barlow with the webcam, and use 2x Orion shorty barlow with the ASI120MM.

I would say if the scope looks good, give him an offer, and see how it goes. I haven't used my C8 for DSO's mainly because I don't think my CG-5 is up to it....and I dont want to dish out for the .63x focal reducer....but plenty of people have used C8s w/ the reducer for DSOs.

Edit: Good call on the crayford focuser. I was never really satisfied with the stock focuser, and picked up a cheap GSO dual speed crayford last month and it is a world of difference in focusing.

#4 yock1960

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Posted 10 January 2013 - 09:25 PM

Make sure the corrector plate has no cracks and the mirror looks fine.


Looks new to me...clean. Both my scopes get crudded up being out catching photons for hours & hours. This looks like it's never been outside!

I would say if the scope looks good, give him an offer, and see how it goes. I haven't used my C8 for DSO's mainly because I don't think my CG-5 is up to it....and I dont want to dish out for the .63x focal reducer....but plenty of people have used C8s w/ the reducer for DSOs.


I plan (if I buy it) to put it on the LXD-75 to do planets. I do have a .63x FR that I bought because it was inexpensive and I couldn't seem to land a William Optics FR for my WO66; that could come in handy.

Edit: Good call on the crayford focuser. I was never really satisfied with the stock focuser, and picked up a cheap GSO dual speed crayford last month and it is a world of difference in focusing.


Got a link for that? My Bahtinov masks are too small also. I try to be frugal...but there is always something else to buy!!!

Steve

#5 Timthelder

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Posted 10 January 2013 - 09:40 PM

As an afterthought,

When I changed my 9.25" SCT on a CG-5 dovetail over to a CGE Pro dovetail, I ordered the wrong one. Mine was an 'American made SCT' which is not the the same as the current China made Synta made SCT.

Mine needed to be fitted with a 'ADM' dovetail. Which is a high quality dovetail, just not a stock dovetail.

In your situation, I would suggest calling OPTcorp and giving them some specs.

If you have to drill some mounting holes for the dovetail rail and tap some threads, (I'm assuming it was 'forked'.) use some cutting oil, the aluminum is some tough stuff.

Also, if you drill, move the primary mirror all the way toward the front of the optical tube to avoid hitting it, there will also be shavings inside the optical tube which will require removal of the corrector plate (if you have to drill, remove it first.)if not you'll have to dump the shavings out.

Mark the corrector plates position and re-install it as it was removed, as I was told they are aligned with the primary mirror.

Been there done that, I hope this helps.

Cheers, Tim.

#6 zAmbonii

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Posted 10 January 2013 - 10:12 PM

Got a link for that? My Bahtinov masks are too small also. I try to be frugal...but there is always something else to buy!!!


This is the one I got from Agena Astro. I am sure they have something similar over at OPTcorp or other places. I also picked up a Bahtinov mask from them during the same order since my mask I made was getting warped and long in the tooth. I picked the one NOT for the SCT, but the one *OD 5.5" to 8.5"*. So I could use it with my 6". It fits at the end of my dew shield, if I needed it...but I rarely use the mask for planetary...with my mount it is really hard to slew to a star, focus, and then slew the target and then get Jupiter on the chip again at the long focal length :).

Oh yea...may want to get a dew shield....and/or dew heater (yea more stuff to buy) :). You can use a hair dryer when the corrector plate fogs up or frosts over, but then you like have to wait 10 minutes for things to equalize again.

#7 yock1960

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Posted 10 January 2013 - 10:22 PM

...but I rarely use the mask for planetary...with my mount it is really hard to slew to a star, focus, and then slew the target and then get Jupiter on the chip again at the long focal length :).


How do you focus then? I tried focusing on Jupiter a little last night; frustrating.

Steve

#8 Timthelder

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Posted 10 January 2013 - 10:44 PM

Use Jupiter's moons...

Cheers

#9 Mert

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Posted 11 January 2013 - 02:43 AM

...but I rarely use the mask for planetary...with my mount it is really hard to slew to a star, focus, and then slew the target and then get Jupiter on the chip again at the long focal length :).


How do you focus then? I tried focusing on Jupiter a little last night; frustrating.

Steve

I normally use a star to focus on, which is the star I
use to do a 1 star alignment ( just sync on it ).
On the star I use the bahtinov mask and focus.
Also with the star centered I adjust my finder scope
such that the star is at the croshairs.
Now slew to Jupiter, won't be far off and center with the
finderscope.
If not on the chip, take the camera out, put an eyepiece
in and center Jupiter, don't touch focus!
Now put the camera in and fine focus o Jupiter,
Works for me :shrug:

#10 jgraham

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Posted 12 January 2013 - 09:55 PM

For several years I used an SC8 at f/30 on my LXD75 for planetary imaging. I used a homemade Bahtinov mask to focus on a bright star, then slewed to the planet. To help with pointing I made an e-finder by mounting my old SPC900NC web cam on an Antares finder. The Bahtinov mask was easy to make using black foam-core art board.






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